
where \(\sigma _{h}^2=\sigma _{AU}^2+M\sigma _{IU}^2\beta _{AI}\) .
The approximation in (REF ) is derived in the appendix of [1]} where it is shown that this approximation becomes more accurate when number of IRS elements is large. blackAlso, it can be easily shown that this approximation remains valid whether the IRS phase shifts are continuous or discrete. 
Without loss of generality, we assume that the effective channel conditions of the first user is better than the second one [2]}, i.e. \(|\hat{\mathbf {h}}^{[1]}\mathbf {w}_{1}|^2\ge |\hat{\mathbf {h}}^{[2]}\mathbf {w}_{2}|^2\) . With this assumption, the following theorem can be presented.
